1. Technical Field
Certain embodiments of the invention relate to a simple planetary reduction gear.
2. Description of Related Art
Japanese Unexamined Patent Application Publication No. 2011-236950 discloses a swiveling apparatus of a construction machine.
The swiveling apparatus includes a simple planetary reduction gear. The simple planetary reduction gear includes a sun gear, a planetary gear which revolves around the sun gear and is supported by a carrier, and an internal gear with which the planetary gear internally meshes, and is used in a vertically installed state, that is, in a state where the shaft center of the simple planetary reduction gear is toward a vertical direction.
The sun gear of the simple planetary reduction gear is integrally and rotatably connected to a motor shaft of a motor via a spline. In the related art, in this kind of simple planetary reduction gear, two methods are suggested in the design of the spline for connecting the motor shaft and the sun gear to each other.
One design is that fitting of the spline is set with interference fitting. According to this design, the support of the sun gear can be completed only on the motor shaft side. A design, in which the sun gear is formed to be directly cut on the motor shaft, is also included in the above-described design.
Another design is that the fitting of the spline is set with clearance fitting.